karst -- n. A type of topography formed by dissolution of rocks like limestone and gypsum that is characterized by sinkholes, caves, and subterranean passages.

karyogamy -- A process of fusion of the nuclei of two cells; the second step in syngamy.

kelp forest -- Marine ecosystem dominated by large kelps. These forests are restricted to cold and temperate waters, and are most common along the western coasts of continents. Kelp forests first appeared in the Miocene.

kettle lakes -- n. Lakes formed as water fills a hole formerly occupied by a block of stranded ice.